Research Of Microbial Community Of Akashiwo Sanguinea And Phycosphere Bacteria Labrenzia Sp. PO1

The increasing recognition of the importance of phytoplankton and bacteria interaction in mechanism of harmful agal bloom(HAB)occurrence,nonetheless,their interactions in mecheanism of HAB are intricate,complex,and dynamic.Our study focused on Akashiwo sanguiea,a commonly observed harmful algae in Shenzhen coast.Here we used both culture-dependent and culture-independent method to analyze A.sanguinea microbial community,Isolated and identified culturable phycosphere bacterium and studied their character;Observed the dynamic change of Akashiwo sanguiea-phycospsere bacteria co-culture by flow cytometry and confocal,our results showed as follow:(1)Rhodobacteraceae were the predominant taxa associated with A.sanguinea in both methods.The dynamic microbial changes in different tested scenarios were determined by Mi Seq sequencing.Rhodobacteraceae,Alteromonadaceae and Flavobacteriaceae were significantly change in response to the state of dinoflagellate.In general,Rhodobacteraceae have a positive impact on the growth of dinoflagellate.Total 15 phycosphere bacterial strains were isolated and identified.(2)The characteristic of phycosphere bacterium were studied,including algicidal activity,biofilm formation,AHL production,antibacterial activity and coculture with A.sanguinea.The results showed that PO1(Labrenzia sp.)secreted antibiotic to prevent algal cell from competitors and thus promote algal growth,while PW(Loktanella sp.)and CW(Pelagibaca bermudensis)produced IAA to enhance algal growth.HK(Alteromonas macleodii)can secreted AHL and have strong algicidal ability.(3)PO1(Labrenzia sp.)was most closely related to Labrenzia aggregate.Cells of strain PO1 were rods,2-4 ?m in size and utilized a wide range of organic carbon sources.The fatty acids comprised 15:0 anteiso(43.9%),17:0 anteiso(18.95%),15:0 iso(13.91%).Whole-genome sequencing was achieved using Pac Bio RS II platform,comprising one closed complete chromosome of 5.8 Mbp with a 59.12 % G+C content.(4)Labrenzia sp.PO1 have a close association with the growth of A.sanguinea,with its abilities of biofilm formation,promoting A.sanguinea growth,antibacterial activity and biosythesing and metaboliting DMSP.We examed the interaction of A.sanguinea and Labrenzia sp.PO1 Dimethylsulfoniopropionate(DMSP)as an abundant organosulfur metabolite produced by A.sanguinea that can regulate gene expression,growth rate and group behavior of Labrenzia sp.PO1.We hypothesize that dimethylsulfoniopropionate is a signal in the interaction of A.sanguinea-bacterium.Our study provided new insights into of mechanism of phytoplankton blooms occurrence.Our study exploited how Dimethylsulfoniopropionate(DMSP)function in the interaction of A.sanguinea and bacterium.These results are the foundations of our ongoing investigations to further understand the interaction of A.sanguinea and its microbial community.